Mining and industrial ecological-geological systems of the Bovanenkovo and South Tambey gas condensate fields and technogenic impact on them

Data on ecological-geological systems (EGS) of the Bovanenkovo and South Tambey fields have been summarized. The Bovanenkovo EGS is located in the central part of the Yamal Peninsula within a flat accumulative-abrasive plain, which is heavily lake-dotted and marshy. A continuous and monolithic distribution of permafrost deposits is observed across the area. The zero isotherm above the gas dome of the Bovanenkovo EGS likely lies at a depth of 170-220 m, and up to 300 m on its periphery. The continuity of the permafrost is disrupted at the surface by non-through thawing areas, and within the profile by lenses of cryopegs and cooled soils. The South Tambey EGS is located in the northeast of the Yamal Peninsula within a flat accumulative plain. Here, a continuous and monolithic distribution of permafrost deposits is recorded. The zero isotherm above the gas dome of the South Tambey EGS likely lies at a depth of 380 m, and up to 440 m on its periphery. Large accumulations of massive ice are extremely widespread in the Bovanenkovo EGS area. The maximum thickness of massive ice here is 28.5 m, and the average thickness is 8 m. The ice masses in the permafrost soils of the Bovanenkovo EGS are so significant that their wide use as underground storage chambers for long-term storage of gas condensate is even planned. The massive ice, ice wedge in the exposures of the ridges and the first lagoon-marine terrace of the South Tambey EGS near the village of Sabetta at various depths, sometimes forming a 2-4 tier ice complex, noticeably complicates the engineering-geological conditions of the area. The thickness of the massive ice, revealed by boreholes, varies from 0.2 to 5.7 m, with an average value of 1.5 m. In August 1978, the author measured the temperatures of frozen soils in boreholes drilled in the floodplain of the Tambey River and compared them with temperatures in boreholes drilled in 2013 on the ridge of the Ob Bay near the village of Sabetta. This comparison showed a significant increase in average annual temperatures over 35 years, amounting to more than 5°C. The data characterizing the features of the techno-ecotope, techno-microbial community, techno-phytocenosis, and techno-zoocenosis of the Bovanenkovo and South Tambey EGS and their technogenic transformation have been summarized. The technogenic transformation of the Bovanenkovo and South Tambey EGS is generally negative, but some components of the EGS show positive trends: a). The territories of the Bovanenkovo and South Tambey EGS are represented by a lithotope of permafrost rocks, consisting of hard-frozen, plastically frozen and cooled soils containing large massive ice, ice wedges, as well as negative-temperature groundwater with high mineralization – cryopegs; b). The experience of developing and operating the Bovanenkovo and South Tambey EGS deposits indicates that, despite attempts to minimize the technogenic impact on the natural environment, the development of fields, as a rule, is accompanied by a relatively rapid and profound change in the geocryological conditions of the territory. Due to strong man-made impacts, a radical change in the thermal state of the soils often occurs - usually their long-term thawing and melting even in areas of low-temperature permafrost development, threatening the stability of the foundations of gas production facilities; 3. The content of polycyclic aromatic hydrocarbons (PAHs) in the snow cover of the South Tambey and Bovanenkovo EGS increases to 2–5 ng/mg. Low-molecular PAHs in the snow of the South Tambey EGS are 0.3–3.9 ng/mg, Bovanenkovo EGS – 1.7 ng/mg, high-molecular PAHs in the snow of the South Tambey EGS are 0.2–1.5 ng/mg, Bovanenkovo EGS – 0.7 ng/mg. The appearance of high concentrations of phenanthrene and anthracene in the PAHs is typical for the snow cover of the recently developed South Tambey and Bovanenkovo EGS. Here, the snow cover reflects the increased industrial load against the background of the overall low level of pollution of the snow cover of the region and the proximity of populated areas. At the same time, the common features for these EGSs are their remoteness from sources of intensive emissions of economic activity in the central region of the Yamal-Nenets Autonomous Okrug and fuel and energy complex facilities; d). Man-made transformation of the edaphotope is mainly expressed in the fact that the construction of main linear systems: pipelines, water mains, heating mains is accompanied by the complete destruction of soils in the corridor of the route; e). The total area of agricultural land withdrawn for the technological facilities of the Bovanenkovo EGS exceeds 5 thousand hectares, i.e. during the period of development of the field, the area of withdrawn lands increased 5 times, and the total area involved in construction, taking into account areas disturbed to varying degrees, increased 20 times. The largest area of withdrawal and disturbance in absolute terms falls on sphagnum and lowland bogs and floodplain willowsж; f). The number of some bird species increases, since in the process of field development the area of suitable habitats expands and additional food sources appear; g}. Uncontrolled fishing as a food product for the sharply increased number of construction workers and gas producers can lead to the depletion of fish stocks; h). Man-made transformation of the zoocenosis due to the creation of the Yamal LNG terminal in the port, and the almost constant open water in the Gulf of Ob, which changed the microclimate that contributes to the formation of an ice shell on the snow, resulted in the fact that the reindeer in the northern part of the Yamal Peninsula cannot break the ice crust with their hooves and get to the lichen, the lack of food for wild and domestic reindeer began to lead to the death of animals; i). Embankments of roads and railways blocking the natural paths of water flows contribute to the formation of swamps, this leads to a reduction in agricultural lands, and also serves as an additional obstacle to the traditional migration of reindeer herds.

permafrost, massive ice, ice wedges, cryopegs, Bovanenkovo ecological-geological system, South Tambey ecological-geological system, technoedaphotope, technomicrobocoenosis, technophytocoenosis, technozoocenosis